Low Earth Orbiting (LEO) satellite networks employ a population of satellites orbiting the Earth at a height, for example, of approximately 100 miles to 1000 miles or higher, with a speed that constantly moves their position relative to the earth surface. Communications from a source terminal to a destination terminal can consist of an uplink transmission from the source to a LEO satellite, for forwarding through a succession of satellite-to-satellite links (also termed “inter satellite” or “ISL”), for downlink by a satellite that is in view of the destination terminal.
LEO satellite networks can provide certain advantages over geostationary earth orbit GEO satellite networks. For example, GEO satellites are positioned approximately 22,200 miles above sea level. Transmitting high bandwidth signals over such distance consumes significant power and, even at the speed radio waves travel, requires substantial time. One “hop,” meaning a “bent-elbow” transmission from the ground to the GEO satellite and back down is a 44,000 mile trip, which requires approximately 250 milliseconds. In certain applications, 250 milliseconds of delay can degrade communication quality.
Communication using a LEO satellite network, in contrast, because of the satellites' low height, consumes far less transmission power. In addition, even when a signal requires multiple hop forwarding through a LEO network to reach its destination, delay from transmission to reception can be substantially less than in GEO systems.
LEO satellite networks, though, have particular complexities that can impose substantial costs in implementation. One large complexity is that unlike a GEO network the topology of a LEO network undergoes constant change. As one illustration, from the perspective of a terminal, the satellites(s) it has in view and can therefore connect to, for uplink, downlink, or both, can change every several minutes. Likewise, from the perspective of any of the satellites, its neighbors are temporary, and therefore ISLs to those neighbors have only a temporary existence. This can contribute to ISL congestion. One result of the changing conditions and topology is that a costly percentage of packets are admitted to the network but dropped, for example, at one of the satellites or at an egress terminal. There can be a secondary cost associated with each dropped packet, namely, the bandwidth of the LEO network that was consumed in the interval from being admitted to being dropped or lost. Improvements in LEO and other mobile node network bandwidth management are therefore needed, for example, in terms of greater average utilization of uplinks, downlinks, and ISLs, and significant reduction in the admission of packets that, ultimately, will be dropped or lost.